The invention relates to a method of forming images of layers of an object. In the method, the object is irradiated from a plurality of radiation source positions in order to form separate single-shadow images. For each single-shadow image, image values are stored in a first memory. The image values depend on the absorption at image points. For each layer image point, a layer image value which corresponds to the absorption of the layer image point is derived from the stored image values of the shadow image points, from a number of images, which are geometrically associated with the layer image point. The invention also relates to a device for performing the method.
A method of this kind is described in U.S. Pat. No. 3,499,146 and from German Offenlegungsschrift No. 3,237,572 (corresponding to U.S. Pat. No. 4,630,296). In the method according to U.S. Pat. No. 3,499,146, the layer image value for an image point of the layer is formed by superposition of the image values of the shadow image points which are geometrically associated with the layer image point. In the method according to German Offenlegungsschrift No. 3,237,572, the layer image value of a layer image point is formed by that shadow image value, of the shadow image points of the single-shadow images geometrically associated with the layer image point, which corresponds to the lowest absorption. Even though the latter method of generating layer images produces more accurate layer images, it still gives rise to artefacts.